For print film, you should be Okay with 1.5v Alkaline batteries. Hearing aid batteries give the correct voltage, and are cheap. They have a short life once used; they produce electricity after being exposed to air.
If you go the Alkaline route, or find a Mercury Cell, you can extend its life by turning the Canonet to manual mode when not in use. That turns the meter off; zero drain on the battery. It will not extend the zinc-air battery, its clock starts ticking when you break the airtight seals.